The instant invention resides in the art of monitoring devices and is more particularly related to such devices for aircraft. It is extremely important that aircraft tire pressure be known to the pilot to reduce the possibility of blowouts. It is well known that the likelihood of a blowout substantially increases with tire pressure changes above or below a particular desired level, and that such blowouts not only result in a loss of the tire itself, but seriously increase the likelihood of further property damage or human injury.
Heretofore in the art, applicant has not been made aware of any tire pressure monitoring systems which will allow a continual monitoring of the tire pressure during both static and dynamic conditions. Brushes have been used in the past to act as commutators for transferring an electrical signal from a rotating to a stationary member. However, "brush dancing" is experienced when used in the environment of an aircraft wheel and noise or spurious signals are generated which substantially reduce the integrity of the sensing system. Further, brushes are subject to contamination in the wheel environment and are generally characterized by an undesirably high resistance path.
The prior art has also taught certain types of interconnections between rotating and stationary members for transmitting tire pressure signals utilizing an induction technique. However, such systems have generally required close tolerances between the static and dynamic coils, which tolerances must not change with movement of the wheel. Accordingly, concentricity problems have made such systems unsuitable for the aircraft industry.
Other approaches to sensing and transmitting electrical signals indicative of tire pressure have utilized magnets maintained within the wheel, operating upon a magnetic field principle. However, problems have been experienced with the carrying of magnets within the wheel due to size and weight requirements. Such systems have generally not been accepted. Similarly rejected as being insufficient have been the tire pressure indicators utilizing apparatus producing an audible signal. However, such systems have been of a nature that a signal is emitted only during the period that the tire is actually going flat or losing pressure. If the operator is not near the tire or vehicle during the period that pressure is being lost, the signal will not be discerned by anyone and the usefulness of such system will be totally lost.
It has therefore become desirably to provide in the art, a tire pressure communication device which provides substantially noise-free output signals while being of sufficiently simplistic nature that it is capable of operating in the severe environment of an aircraft wheel without reduction of system integrity.